Ultrastructural localization and characterization of a ribosomal antibody detected by immunofluorescence in systemic lupus erythematosus.

The ribosomal antibody detected by tissue immunofluorescence in about 1% of SLE patients was conjugated with peroxidase and its antigen localized by immunoelectronmicroscopy, using rat stomach as substrate. The antibody stained ribosomes on rough ER, single ribosomes and polyribosomes, but not membranes. Gastric chief cells reacted most intensely; ribosomes in plasma cells, lymphocytes and eosinophils seen between gastric cells were also positive, thus confirming earlier immunofluorescence studies which showed that all tissues react in relation to their ribosomal content. Nucleolar ribosomes were unreactive. The ribosomal antigen was resistant to glutaraldehyde, formaldehyde, acetone, ether, ethanol, methanol and detergents such as deoxycholate. Digestion of the sections with RNase did not diminish the immunofluorescence. Trypsin could not be used on sections but is known from previous CFT studies to destroy the ribosomal antigen. It was concluded that this antigen is a ribosomal protein unlike other tissue autoantigens of which several studied so far are lipoprotein in nature.